1. Field of the Invention
The present invention relates generally to coin sensors for validating a coin in a coin accepting machine, such as a vending machine, and more particularly to a sensor for evaluating the diameter of the coin. For purposes of the following disclosures, the term xe2x80x9ccoinxe2x80x9d is used generally to refer to monetary coins, tokens, and the like.
2. Description of the Related Art
A coin sensor and a decision circuit of a coin selector are detailed with reference to FIGS. 18 and 19. The sensor is formed within a body 50 and includes a coin acceptance slot 51 leading to a coin passage 52. The coin passage 52 is comprised of peripheral guidewalls 53, 54 and sideplates 55, 56. The sideplates 55, 56 extend parallel to a diameter of the coin C, and the guidewalls 53, 54 are located at opposed ends of the sideplates as shown in FIG. 19 to form a rectangular profile. A line L illustrating the path of the coin C lies in the vertical direction.
The distance between the peripheral guidewalls and between the sideplates are selected to accommodate several different sizes of coins. Accordingly, the space between the peripheral guidewalls 53, 54 is slightly larger than the largest diameter coin anticipated to be used in the sensor. Similarly, the space between the sideplates 55, 56 is slightly larger than the thickness of the largest coin that is to be used.
A first coin sensor 57 is located on a horizontal line M that intersects the path line L in a perpendicular manner. The coin sensor 57 lies along the coin passage 52 adjacent the sideplate 55. Sensor 57 comprises a wound coil 57C about a cylindrical core 57B. The core 57B is preferably made of a ferromagnetic material, such as ferrite.
A sensor 60 is fixed opposite the sensor 57 on sideplate 56. Sensor 60 comprises a wound coil 60C about a cylindrical core 60B. Another sensor 61 is mounted on the sideplate 55 adjacent the peripheral guidewall 54. The center of sensor 61 is also located on line M. Sensor 61 comprises a wound coil 61C about a cylindrical core 61B. Sensor 62 is mounted opposite sensor 61 at sideplate 56. Sensor 62 comprises a wound coil 62C about a cylindrical core 62B. The sensor pair 57, 60 cooperate to form a coin left end sensor 63 used to determine the relative area of the left end of the portion of coin passing by sensor 63. Similarly, the pair of sensors 61, 62, cooperate to form a coin right end sensor 64 and is used to determine the relative portion of the coin passing by the right end sensor 64.
Sensors 65, 66 lie along path line L and are offset from line M. Sensors 65, 66 are similar in structure to sensor 61 in that each sensor 65, 66 includes a coil 65C, 66C, respectively, wound about a cylindrical core 65B, 66B, respectively. The sensors 65, 66 constitute a material sensor 67 and a thickness sensor 68.
A coil 65D is wound around the outside of coil 65C. The coil 65C is connected to the coil 66C. Similarly, the coil 65D is connected to the coil 66D. The thickness sensor 68 comprises the coil 65C wound about the core 65B. The material sensor 67 comprises the coil 65D and 66D about the respective core 65B and 66B. A beginning end of coil 57C is connected with the termination end of coil 61C. The termination end of coil 57C is connected with the termination end of coil 60C. A starting end of coil 60C is connected with a termination end of coil 62C. A starting end of coil 62C is connected to an oscillation circuit 70, and a starting end of coil 61C is connected to the oscillation circuit 70.
The end of the coil 65C of the thickness sensor 68 is connected to the oscillation circuit 71. A starting end of the coil 65C is connected to the termination end of the coil 66C of the sensor 66. A starting end of the coil 66C is connected to the oscillation circuit 71.
A starting end of the coil 65D of the material sensor 67 is connected to the oscillation circuit 69. A termination end of the coil 65D is connected with the termination end of the coil 66D of sensor 66. A starting end of the coil 66D is connected to the oscillation circuit 69. The oscillation circuit 69 is connected with a detection circuit 72. An oscillation circuit 70 is connected to a detection circuit 73. The oscillation circuit 71 is connected with the detection circuit 74.
The detection circuits 72, 73, 74 are respectively connected to a control circuit through AD connection circuits 76, 75, 77. The control circuit comprises a microprocessor 78. The unit also includes a reject board 80 which obliquely crosses the path line L of the coin passage 52.
The coin C is deflected by the reject board 80 when the reject board 80 protrudes in the pathway defined by the coin passage 52. A coin return (not shown) is found at the end of the rejection passage 81.
The movement of the reject board 80 is controlled by a spring (not shown) generally, which biases the position of the reject board 80 into and out of the pathway of the coin passage 52. The control is governed by a solenoid 82 excited by the signal of the microprocessor 78, when the microprocessor determines that the coin is unacceptable. By the excitation of the solenoid 82, the reject board 80 is withdrawn from the coin passage 52 when it is determined that the coin is acceptable. In this case, the coin falls past the reject board 80 into a coin collection unit (not shown).
The foregoing describes a coin sensor which may be used, for example, in a vending machine. A coin C dropped into the receiving slot of a vending machine reaches the coin passage 52. As the coin falls vertically, the coin passes left end sensor 63 and right end sensor 64 to varying extents depending on the path of the coin, i.e., whether the coin falls down the center or toward one side. As the coin passes the sensors, a high frequency is applied from the oscillation circuit 70 to the coil 57C and 60C of the left end sensor 63 and the coil 61C and 62C of the right end sensor 64. A resultant magnetic flux is generated at the cores 57B, 60B, 61B and 62B. The magnetic flux from each core extends into the coin passage 52. Eddy currents are generated in the coin C when the coin (an electrical conductor) passes through these magnetic flux. As a result, the magnetic flux of the coils 57C, 60C, 61C and 62C are reduced.
The loss of flux due to the passing of the coin causes a change in the output of the oscillation circuit 70. The flux loss is proportional to the relative area of the coin C adjacent the respective cores 57B, 60B, and 61B, 62B. The detection circuit 72 converts an output of the oscillation circuit into a voltage. The AD conversion circuit 75 output of the detection circuit 73 is converted into a digital value that is transmitted to microprocessor 78.
Similarly, a magnetic flux arising in the coil 65C at the core 65B is affected by the thickness of the coin C. A magnetic flux arising from the coil 66C at the core 66B is affected by the thickness of the coin C. As a result, an output of oscillation circuit 71 changes. The digital circuit 74 converts an output of the oscillation circuit 71 into a voltage. The AD conversion circuit 77 output of the detection circuit 74 is converted into a digital value, and is transmitted to the microprocessor 78.
A magnetic flux generated by the coil 65D at core 65B is affected by the material at the interior of the coin C. Similarly, a magnetic flux generated by the coil 66D at the core 66B is affected by the material at the interior of the coin C. As a result, the output of the oscillation circuit 69 varies. The detection circuit 72 converts an output of the oscillation circuit 69 into a voltage. The AD conversion circuit 76 output of the detection circuit 72 is converted into a digital value, and it is transmitted to the microprocessor 78.
The microprocessor 78 determines whether the coin C is of a particular acceptable diameter based on information stored in the memory 83. That is, the voltage from the AD conversion circuit 75 is compared with a reference value to a known diameter coin determined beforehand and stored in the memory. The microprocessor 78 also distinguishes whether the material in the coin C is an acceptable material based on stored values. The voltage from the AD conversion circuit 76 is compared with reference values stored in memory 83 to evaluate the material. A microprocessor 78 also distinguishes whether the thickness of the coin C, based on the voltage from the AD conversion circuit 77, is acceptable compared with reference values stored in memory 83.
When the microprocessor 78 determines that the diameter, material, and thickness of the coin C is acceptable, the microprocessor 78 excites the solenoid 82. This excitation causes the reject board 80 to be withdrawn from the coin passage 52 such that the coin can fall into the retention reservoir (not shown).
If the microprocessor determines that there is a deviation in the acceptable thickness material, or diameter from the provided reference values, then the solenoid 82 is not excited. The rejection board 80 remains in the pathway between the coin passage 52 and the retention reservoir. The coin is thus deflected by the rejection board 80 into the cancellation passage 81, where it is led to a coin return.
The width W (FIG. 18) of the coin passage 52 is selected to accommodate coins of various types. To accomplish this, the width is selected to be slightly bigger than the diameter of the largest coin anticipated to be used with the coin selector. As a result, the position of the coin passing along the coin passage 52 is unknown beforehand.
For example, consider the case in which the coin C having the diameter shown in FIG. 20A travels along the central portion of the coin passage 52 as shown. At the point at which the coin falls directly and equally between the two sensors, the coin covers more than three quarters of the circular areas of cores 61B, 62B and of cores 57B, 60B. The covered portion of the two sensors is indicated by the hatched region, and the uncovered portion of the core""s areas are unhatched.
In the case illustrated in FIG. 20B, the coin passes closer to the sensors 57, 60, than the sensors 61, 62. In this case, the cores 57B, 60B are almost completely covered by the coin C, whereas about half of the cores 61B, 62B are covered by the coin C. As a result, the relative area for the coin C covering the portion of core 61B, 62B is decreased in comparison with the first case shown in FIG. 20A. To compare the areas left uncovered between FIG. 20A and FIG. 20B, the two slices of area from FIG. 20A is superimposed over the uncovered area of FIG. 20B in cross hatching. The difference in the total area left uncovered by the coin in FIG. 20B can be seen to be greater than the area left uncovered in FIG. 20A.
As a result, the output of the detection circuit 73 becomes line v, as it is shown in FIG. 21 when the coin falls to the left as shown in FIG. 20B. When the coin falls down the center of the passage 52, the output of the detection circuit 73 is shown by line V, and xcex94V1 is the voltage difference between the two cases. In FIG. 22, a similar case in which a smaller coin is explained with the same conditions as FIG. 20.
In the case in which the small coin c falls to the left of the passageway as shown in FIG. 22B, the relative area of the cores 57B, 60B, and 61B, 62B covered up by the coin C increase and decrease, respectively, in comparison with the case in which the coin falls directly down the middle as shown in FIG. 22A. The superimposed cross-hatched area in FIG. 22B from the areas of coverage in FIG. 20A illustrates the difference between the two cases.
As a result, the voltage is shown by line Y in FIG. 23 when the coin falls to the left side as shown in FIG. 22B. The voltage is shown by line y when the coin falls down the center of the passage 52, and xcex94V2 is the voltage difference between the two cases. The potential difference of xcex94V1 and xcex94V2 arises from the size of the coin and the path that the coin travels down the passage.
This tolerance associated with the voltage as a result of the path taken by the coin makes the threshold determination of the coin""s verification difficult. That is, the evaluation that determines an acceptable coin as compared with a unacceptable coin is improved when the tolerance of xcex94V is small. Conversely, the rate at which the sensor incorrectly judges the authenticity of the coin increases when the tolerance is large.
The purpose of the present invention is to improve the selection performance of the coin sensor. This is achieved by the present invention in which the output of the sensor does not change regardless of the passage that the coin travels through the passageway.
To achieve this objective, the coin selector of the present invention comprises a coin passage for guiding a coin, a first sensor and a second sensor adjacent the coin passage, both the first sensor and second sensor comprising a coil wound about a core, where the core of the first and second sensor is shaped to have substantially straight and parallel upper and lower boundaries, such as a rectangle or square.
It is preferable that the coin passage is vertically oriented. In the present invention, it is preferable that the coin passes the core of the sensors such that the sensor reads the width of the coin. In reading the width of the coin, the area difference by the curvature of the circular arc of the coin is small. This allows for a common discrimination standard among multiple coins.
Also in a preferred embodiment of the present invention, a coin passage in which a coin is guided includes a first sensor and a second sensor which are adjacent the coin passage, said first coin sensor laterally offset of the center of the coin passage, a third coin sensor that is located opposite the first coin sensor, said second coin sensor laterally offset from the center of the coin passage, a fourth coin sensor that is located opposite the second coin sensor, where the first, second, third and fourth coin sensors are each comprised of a coil wound about a core in the shape of a rectangle when viewed from the coin passage.
When the coin passes the cores of the previously described sensors, an equal voltage output is derived, regardless of the passage path that the coin takes. Therefore, the detection accuracy of the coin is improved.